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Mon, May 3

Speaker: Xun Niu, PhD (Postdoctoral Candidate)

Title: Multi-finger Prehension Synergy: Stability and Inverse Optimization

Abstract: The results of two research projects will be briefly presented: (1) Effects of transcranial magnetic stimulation (TMS) on stability of multi-finger prehension, and (2) Analytical Inverse Optimization (ANIO) of finger forces in multi-finger prehension.

  1. The control of hand action is commonly viewed as based on a two-level hierarchy (higher level: thumb and Virtual Finger; lower level: individual fingers). The synergies at both levels can be studied as patterns of co-variation of its elements to stabilize the overall output. In an experiment involving single-pulse transcranial magnetic stimulation (TMS) as a perturbation to multi-finger grasping, the stability of the three components of the prehension synergies was explored: (a) internal forces, (b) resultant force, (c) moment of force exerted on the hand-held object.
  2. The classical optimization problem consists in finding the values that minimize a given objective function while satisfying known constraints, while an inverse optimization problem consists in finding an unknown objective function to predict solutions. Recently, an Analytical Inverse Optimization (ANIO) method of finding the cost function from experimental observations has been developed in our lab (published in the Journal of Mathematical Biology, 2010). The core of the method is the Uniqueness Theorem that provides sufficient conditions for the uniqueness of solutions of the inverse optimization. An ongoing research on the application of the ANIO method to determine the cost function presumably used by the CNS for sharing the grasping force in multi-finger prehension will be described.

Host: Mehdi Mirbagheri